Brush holder for rotary electric machines



March 4, 1958 A. FRANCK 2,825,831

BRUSH HOLDER FOR ROTARY ELECTRIC MACHINES Filed April 7, 1955 HQLDER FUR ROTARY ELECTRIC MAQHINES nnusn Ventilation and cooling of the brushes in rotary electric machines, particularly motors of the so-called universal types, are a continual source of trouble for manufactnrers.

l'n machines currently built, the brushes are generally enclosed in a brush-carrier sleeve or bushing. As a result, the heat generated by friction of the brush against the armature collector ring cannot be dissipated. H

A general object of the present invention is to provide improvements in rotary electric machines, whereby the ventilation of the brushes is improved and their service life thereby lengthened.

Another object of the invention is to provide a highly simple construction whereby the number of parts employed and the amount of labor required for assembly are reduced.

A further object of the invention is to mold the casing of a rotary machine from a thermoplastic synthetic resin thereby reducing the rise of temperature in service of the component parts.

Further features and advantages of the invention will appear from the ensuing description made with reference to the accompanying drawings, given by way of example but not of limitation, and providing a clear understanding of the manner in which the invention may be performed.

Fig. 1 is an isometric view of one embodiment of a brush mounting arrangement wherein a hexagonal cross section shaped brush is put between three plane surfaces;

Fig. 2 is a sectional view of said embodiment;

Fig. 3 is a sectional view of an alternative embodiment of a brush mounting arrangement wherein the brush is of pentagonal cross section shaped;

Fig. 4 is a sectional View of another alternative embodiment of a brush mounting arrangement, wnerem the brush has a square cross section and is guided by two angie shaped arms, the inner surfaces of which include two opposite arrises of said brush;

Fig. 5 is an isometric view of another alternative embodiment of a brush mounting arrangement, wherein the brush has a square cross section and is guided by two angle shaped arms, the inner surfaces of which include two consecutive arrises of said brush and by a plate, the inner surface of which is adjacent the area opposite at the areas adjacent said consecutive arrises;

Fig. 6 is a sectional view of said embodiment;

7 is a sectional view of another brush mounting, wherein the brush is pierced by a duct and the support element slides into said duct.

The body or casing of the motor selected as an example of a rotary electric machine, to which the invention is applicable, may conventionally comprise a cylinder of electrically insulating material, such as the plastic known as Pollopas, and is adapted for receiving therein the inductor or field elements, with an armature secured on a collector-carrying shaft mounted for rotation centrally thereof.

2,825,831 Patented Mar. 4, 1958 To facilitate the understanding of the drawings, and in view of the conventional character of the general layout just set forth, the inductor, armature shaft and collector have not been illustrated.

As will appear from the drawings, an electric motor embodying the improvements of this invention comprises a cylindrical casing 2 as just indicated, having secured thereto as many supporting brackets 3 or bracket assemblies (3a, 3b, 3c, 3d, inthe various embodiments) as there are provided brushes 1 in said motor.

Referring to Figs. 1 and 2, the brush it is of prismatic shape (e. g. of hexagonal cross section as shown) and is supported and guided by three plate arms 3e, 3 3g, secured to the casing 2 at one end thereof, and their inner surfaces extending, so as to define therebetween a kind of duct of prismatic shape complementary to that of the brush 1, in a direction such that the longitudinal axis of the brush lies on a radial line of the casing. Desirably these supporting means are molded integrally with the casing 1.

The brush 1 is urged towards the center of said casing by a spring 4 having its rear end seated against the inner wall surface of the casing 2. In order to retain the ng in a centred condition, there is provided a stud .1 integrally connected with the circular wall and projecting therefrom normally to the wall surface.

Referring to Fig. 3, the brush 1a is of pentagonal cross-section.

The brush 1b shown in Fig. 4 has quadrangular cross section and slides between two angle shaped arms 312 and 3f secured to the casing 2 at one end thereof. The inner surfaces of said shaped arms Sit and 3 include two opposite arrises of said brush.

According to the form of construction illustrated in Figs. 5 and 6, the brush 1c of square cross section slides in a kind of duct of square shape formed by the inner surface of two angle shaped arms 3:: and 3b and a plate 3m. The inner surface of said angle shaped arms 3a and 3b includes two consecutive arrises of said brush and the plate 3m slides along the area opposite at the areas adjacent said consecutive arrises.

All said supporting means 3a, 3b, 3c 3m being molded integral with the casing 2, said supporting means may be disposed so as the casing and said supports can be taken from the mould. For this, it is necessary that the biggest size L of a support 3 (see Fig. 2, 3 or 6) is smaller than the distance D between two consecutive supports.

According to the form of construction illustrated in Fig. 7, the brush 1 is formed with an axial duct 1a preferably prismatic in shape (e. g. with a square section as shown). The casing 2 is formed with a radial appendage 3 formed with a complementary prismatic cross section fitting slidably into the duct 1a. A spring 4 abutted against the inner wall of the body 2 tends to push the brush towards the centre of the structure. It will be understood that the appendage 3 may either be moulded integral with the casing 2.

It will readily be observed that in the constructions of Figs. 1 to 6 the brush is isolated from the surrounding atmosphere only in small areas adjacent the supporting element, whereby a maximum surface area is made available for adequate cooling.

In the construction of Fig. 7, the brush is even more efliciently ventilated since no part at all thereof is isolated from the atmosphere.

The intense cooling thus made possible leads to a more efiicient operation of the brushes and increased life thereof, while at the same time it makes it possible to mold the casing 2 and supports or brackets 3 from thermoplastic synthetic resins which are usually imprac- 3 H ticalnto use owing to the high temperatures to which these parts are apt to be subjected in service as a result of the poor ventilation in conventional brushes.

What I claim is:

1. In a rotary electric machine, a substantially cylindrical outer casing, brushes of polygonal cross-section, and for each brush a plurality of spaced supporting members connected with one of their ends to the inner surface of said casing, the inner surfaces of said supporting members defining between each other a ventilated duct having a polygonal cross-section conforming to the cross section of said brushes, said brushes being slidably arranged in said ducts.

2. A device as claimed in claim 1, wherein said supporting members form at least three spaced plane surfaces defining said duct.

3. In a rotary electric machine, a substantially cylindrical outer casing, brushes of quadrangular cross-section, and brush holders, each brush holder comprising two spaced L-shaped arms extending radially inwardly r g 7 from said casing and engaging diametrically opposite corners of said brushes, said brushes being slidably arranged in said holders.

4. In a rotary electric machine, a substantially cylindrical outer casing, brushes of quadrangular cross-section, and brush holders, each brush holder comprising two spaced L-shaped brackets and one flat bracket extending radially inwardly from said casing, said L-shaped brackets engaging opposite corners of one side of said brushes and said flat bracket supporting the opposite side of said brushes, said brushes being slidably arranged in said holder. 7

References Cited in the file of this patent UNITED STATES PATENTS 1,239,056 Sparks Sept. 4, 1917 2,454,230 Stickney Nov. 16, 1948 FOREIGN PATENTS 617,387 Great Britain Feb. 4, 1949 

